Fix auto pricelist resolution and latest-price selection; update Bible

bible/02-architecture.md

@@ -118,6 +118,26 @@ A configuration can reference up to three pricelists simultaneously:
 
 Pricelist sources: `estimate` | `warehouse` | `competitor`
 
+### "Auto" Pricelist Selection
+
+Configurator supports explicit and automatic selection per source (`estimate`, `warehouse`, `competitor`):
+
+- **Explicit mode:** concrete `pricelist_id` is set by user in settings.
+- **Auto mode:** client sends no explicit ID for that source; backend resolves the current latest active pricelist.
+
+`auto` must stay `auto` after price-level refresh and after manual "refresh prices":
+- resolved IDs are runtime-only and must not overwrite user's mode;
+- switching to explicit selection must clear runtime auto resolution for that source.
+
+### Latest Pricelist Resolution Rules
+
+For both server (`qt_pricelists`) and local cache (`local_pricelists`), "latest by source" is resolved with:
+
+1. only pricelists that have at least one item (`EXISTS ...pricelist_items`);
+2. deterministic sort: `created_at DESC, id DESC`.
+
+This prevents selecting empty/incomplete snapshots and removes nondeterministic ties.
+
 ---
 
 ## Configuration Versioning